A critical comparative review: Analyzing limitations, modification strategies and mechanisms of photocatalysts for toluene oxidation.

Abstract

The intrinsic limitations of semiconductor photocatalysts hinder their efficient application in organic transformations. Previous reviews have mainly focused on general photocatalytic oxidation processes, reaction mechanisms, and TiO2-based systems, providing valuable insights into reaction intermediates and catalytic pathways. However, a comprehensive understanding of how different semiconductor families overcome intrinsic limitations through specific modification strategies and how these strategies regulate structure-property-performance relationships remains lacking. This review critically evaluates the limitations of major semiconductor photocatalyst families and systematically analyzes advanced engineering strategies, including doping, heterojunction construction, defect regulation, and structural modification, for enhanced toluene oxidation. Particular emphasis is placed on how these strategies influence electronic structures, charge migration, surface reactions, and overall catalytic performance. Furthermore, a multi-parameter comparison of modified catalysts is provided to reveal the balance among light absorption, charge separation, surface activity, conversion efficiency, and selectivity. Mechanistic insights supported by advanced characterization techniques, including electron paramagnetic resonance (EPR/ESR), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS/FTIR), and density functional theory (DFT) calculations, are integrated to elucidate reactive species generation, surface interactions, and structure-activity relationships. By connecting modification strategies with catalytic outcomes, this review provides critical design principles for developing efficient and selective photocatalytic systems for toluene oxidation.